Until now, inter-node distance measurement devices have measured the distance from a node station that is part of a bus type field network by measuring the period of time until a response is received after transmitting a command to each node station connected to a network cable and then specifying the distances to each of the node stations on the basis of the measured period of time.
In practice, because the variation in performance specific to the communication IC (integrated circuit) of each node station is large, cases occur in which the distance specified on the basis of a measured time difference between the transmitted command and the received response differs from the actual distance. To solve this problem, for example, the technique described below and disclosed in Patent Literature 1 improves the measurement accuracy by repeating the measurements multiple times (N times) and then performing an averaging process on the N measurement values obtained.